The invention relates generally to minimally invasive surgical tools and techniques and, particularly, to a method and apparatus for cutting body tissue using a bipolar or monopolar electrocautery tool with rotational cutting blades.
Minimally invasive surgery such as laparoscopic, endoscopic, hysteroscopic, and arthroscopic surgery is becoming more widely used because it is less traumatic to the patient, generally involves less hospitalization time, less discomfort and less risk to the patient, and can be less costly than traditional open surgery. A minimally invasive surgical procedure is typically performed by making a small incision in the patient which provides access to the area to be treated. A trocar sheath may be inserted in the incision and an airtight seal around the trocar established. The area in the body which is to be treated may be dissected from surrounding tissue by a dissecting tool such as a balloon dissection tool. The dissecting tool is then removed and an elongated surgical tool is inserted through the trocar sheath. Access to the area to be treated may be through one or more trocar sleeves which may be configured to permit the slidable insertion of the endoscopes and surgical instruments without compromising the airtight seal around the trocar sheath.
Minimally invasive surgery is generally performed using elongated instruments slidably inserted through the trocar sleeves, or if the surgery is performed in a naturally occurring body cavity, such as the uterus, the instruments may be inserted through a relatively narrow body orifice such as the cervix. In any event, the operator must perform the surgical manipulations using a tool such as a scalpel or a needle gripper on the end of the elongated surgical instrument. The tool is remotely located from the operator""s hands and confined within a relatively small cavity created for the operation. The elongated surgical tool is often endoscopic, i.e., it includes a camera by which the surgeon can observe the area in the body that is to be treated.
FIG. 1 shows prior art pivoting scissors 190 that can be used for surgery. Pivoting blades 192 and 194 of scissors 190 are pivotally attached to an elongated shaft 196 at a pivot point 198. The scissors 190 have a width W when blades 192 and 194 are fully open. The pivoting scissors 190 can be controlled by cables (not shown) that extend through shaft 196. The cables are connected to a pistol grip 191 at the opposite end of shaft 196 that has a lever 193 that is squeezed by the operator. The lever 193 has a lever arm which produces a magnification of the force applied by the operator at the pistol grip 191 and transmitted through the cables to the blades 192 and 194. The pivoting scissors design of FIG. 1 does not provide an opening or a lumen through shaft 196 for an auxiliary instrument such as an endoscope or an irrigation or suction cannula. Thus, pivoting scissors 190 generally do not allow additional instruments to be used through the same incision.
The surgical manipulations must be performed while observing the procedure with an endoscope or other imaging device. The imaging device may be inserted through a separate trocar into the distal cavity. Alternatively, the endoscope may be contained within a surgical tube which also contains surgical instruments. The image from the endoscope is often displayed on a video screen and generally results in an image having little or no depth perception.
One example of an increasingly common minimally invasive surgical procedure involves the xe2x80x9charvestingxe2x80x9d of a saphenous vein as part of a heart bypass operation. The saphenous vein can be removed from the leg of a heart bypass patient and then used on the heart to provide the bypass vessels. One method of harvesting a saphenous vein involves making an incision along nearly the entire length of the patient""s leg and then removing the saphenous vein by open surgery. This technique can create great discomfort to the patient and increase the risk of complications because of the length of the incision and the open surgery. Also, after such a surgery, the time required for the patient to heal is relatively long.
Another technique commonly used for saphenous vein harvesting involves a minimally invasive procedure that requires two incisions; the first incision being either at the knee area or the ankle area, and the second being at the top of the patient""s leg near the groin area. Through one incision, the surgeon inserts a first instrument such as the elongated scissors shown in FIG. 1, and through the other incision, the surgeon inserts a second instrument such as an elongated clamp or a ligating tool. After inserting the two instruments, the surgeon holds one instrument in one hand and the other instrument in the other hand. The surgeon then simultaneously manipulates the instruments to perform the surgical procedure. For instance, the surgeon holds a piece of tissue such as a blood vessel with the clamp, and then cuts the blood vessel with the scissors. This technique, even though it is less invasive than an open incision, is cumbersome for the surgeon to accomplish because the surgeon must manipulate two separate instruments from two different directions or positions.
Also, the two-incision technique is difficult because the surgeon must observe the instruments and tissue in the body cavity from two different directions. When each instrument is accompanied by an endoscope, each endoscope provides an image of the end of the other tool as it moves toward the endoscopic lens from the opposite direction. Even in a single-tool procedure in which the elongated surgical instrument is inserted through the first incision and an endoscope is inserted through the second incision, the endoscope provides an image of the end of the elongated surgical instrument as the surgical instrument is moving toward the endoscope. The surgeon must interpret this counter-intuitive image while manipulating the surgical instrument.
When a saphenous vein is harvested using any of the aforementioned techniques, the main vessel that will be removed must be separated from tributary vessels that branch off the saphenous vein along its length. Before the vessels are cut, they are typically ligated by applying a clip, for example. After the tributaries are cut away from the saphenous vein, they must be permanently closed. This can be accomplished by suturing, clipping, or cauterizing. Each of these ligation techniques requires a separate step, which increases the time required for the surgery.
Surgical procedures can be improved so as to decrease patient discomfort and hospitalization time by techniques that combine the cutting and ligating or cauterizing procedures. One such technique is electrocautery. An electrocautery tool typically includes a scalpel or the blades of scissors that are electrically energized. Electrocautery can be used to simultaneous cut and cauterize tissue.
Methods for improving minimally invasive surgical procedures include decreasing the size of the instrument or performing the procedure through fewer incisions. Decreasing the size of the instrument or reducing the number of incisions reduces the damage caused to the patient""s body and tissues, thus reducing the time required for healing.
An embodiment of the present invention includes a surgical instrument having a tube and a shaft within the tube. The tube and the shaft each have a distal end and a proximal end. The distal end of the tube includes a cutting edge, and the distal end of the shaft includes a blade. Either the blade or the shaft is rotatable with respect to the other such that the blade cooperates with the cutting edge to cut body tissue.